The invention disclosed and claimed herein falls generally within the field of mechanisms for coupling and locking cargo containers by means of standard fittings on the containers. More particularly, the invention pertains to the field of twist locks for coupling and securing cargo containers having standard fittings. Even more particularly, the invention pertains to such mechanisms which are adjustable in height and which are adapted to lift a container as well as to secure it so that a raising force can be applied to the container at the fitting by the locking mechanism.
Shipping containers are widely employed in the portage industry to facilitate the handling, storing, and transporting of cargo. In order to secure the containers while they are being transported and to move them during handling, a number of methods and mechanisms have been developed.
One set of mechanisms includes a fitting of standard dimensions which is integrated into a cargo container at its corners to provide points of attachment for securing and lifting. Other mechanisms have been developed to provide a locking interface at the fittings. The most common of these locking mechanisms includes a retractable piece which may be inserted into an opening in the fitting after which a rotatable locking element is turned to provide a retaining force between the fitting and the mechanism.
Representative locking mechanisms with retractable twist locks are disclosed in U.S. Pat. No. 3,521,845, U.S. Pat. No. 3,701,562, U.S. Pat. No. 3,749,438 and U.S. Pat. No. 3,924,544. Such mechanisms comprise a shaped member for engaging a fitting opening and for resisting shear forces when the mechanism is in place. The shaped member generally is combined with a shank which carries a flange. Rotation of the shank to one position will cause the flange to contact an inner surface of the fitting to provide a retaining force; rotation to another position will allow the flange to clear the fitting opening and be retracted therefrom. A jack mechanism is provided for inserting the member and locking mechanism combination into the fitting opening and for withdrawing it therefrom. The locking mechanism is held at a position by means of a member which extends laterally from the shank to engage a restraining device at a distance from the shank.
In all of the prior art devices the locking mechanism has a single function: to provide an attachment interface for a container. None of the devices provides the added function of lifting a container which would be convenient when moving it with a forklift. All of the mechanisms described in the prior art provide for a vertical adjustment of the locking mechanism. However, this adjustment feature merely allows adaptation to fittings having different wall thicknesses. None of the prior art locking mechanisms provides a surface for supporting the container in the area of the fitting which can translate the vertical adjustment to a lifting force.
In addition, the mechanical structures of the prior art devices are broadened in a lateral direction in order to accommodate various latching assemblies. The result is a device which is larger than necessary to perform the attachment function.